In this application we combine the efforts of two long term studies investigating the neural mechanisms of tactile spatial perception. Dr. James Craig of Indiana University will not be renewing his grant but instead will be joining this project at Johns Hopkins University. The broad goals of this application are to understand how two-dimensional shape, texture and motion are represented in somatosensory cortex. Shape, texture and motion are important in all sensory systems. We will use a 400-probe stimulator that can produce a wide range of dynamic patterns to stimulate the finger pad. We will perform both psychophysical studies in humans and neurophysiological studies in non-human primates. The first aim is to understand how complex patterns are perceived and represented in somatosensory cortex. In these experiments we will investigate how spatial features such as lines and curves are combined both spatially and temporally to from complex spatial patterns. The second aim is to investigate how texture is represented in somatosensory cortex. In these experiments, we will use a wide range of spatial patterns that we used previously to study the peripheral mechanisms of texture perception to determine how texture is coded in cortex. The third aim is to investigate how motion is represented in cortex. In particular we will scan various spatial patterns across the finger pad at different directions and scanning velocities to determine how motion interacts with form and texture processing. The results from these studies will provide an understanding of the mechanisms underlying central neurological problems and will provide an understanding of the sensory feedback that is necessary for the control of prosthetic limbs. A third benefit is that these studies will aid in the development of cutaneous communication systems for the deaf and blind. PUBLIC HEALTH RELEVANCE: The results from the proposed studies will aid our understanding of the effects of both peripheral and central neurological problems, and our interpretation of the results of neurological examinations, such as changes in light touch thresholds, spatial acuity, and directional sensitivity. To provide sensory feedback for the control of prosthetic limbs, it is important to understand how the hand normally processes touch information. In addition, the proposed measures of the perceptibility of tactile patterns will aid in the development of cutaneous communication systems for the blind, deaf, and deaf-blind.